UNIVERSITY  OF  CALIFORNIA 

COLLEGE    OF    AGRICULTURE 

AGRICULTURAL    EXPERIMENT    STATION 

BERKELEY,    CALIFORNIA 


MACHINES  FOR  COATING  SEED  WHEAT 
WITH  COPPER  CARBONATE  DUST 


BY 

A.  H.  HOFFMAN  and  H.  L.  BELTON 


BULLETIN  391 

September,  1925 


UNIVERSITY  OF  CALIFORNIA  PRINTING  OFFICE 

BERKELEY,  CALIFORNIA 

1925 


Digitized  by  the  Internet  Archive 

in  2012  with  funding  from 

University  of  California,  Davis  Libraries 


http://www.archive.org/details/machinesforcoati391hoff 


MACHINES  FOR  COATING  SEED  WHEAT 
WITH  COPPER  CARBONATE  DUST 

By  A.  H.  HOFFMAN  and  H.  L.  BELTON 


Several  years'  use  of  copper  carbonate  dust  on  seed  wheat  has 
proved  conclusively  that  when  properly  applied  it  is  an  almost 
absolute  preventive  of  bunt  or  stinking  smut  and  yet  that  it  does  not 
in  the  least  injure  the  seed.  Many  means  have  been  devised  for 
applying  this  fungicide,  only  some  of  which  have  fully  met  the 
requirements. 

Requirements. — A  machine  for  this  purpose  should: 
1.  Coat  each  kernel  completely.    Viewing  with  a  good  magnifying 
glass  a  representative  sample  of  the  treated  grain  will  determine  how 
well  this  has  been  done.     (See  fig.  1.) 


Fig.  1. — A  magnifying  glass  should  show  that  every  portion  of  the  surface 
is  covered.     Group  (1)   satisfactory,  (2)   untreated,   (3)  unsatisfactory. 


4  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

2.  Allow  little  or  none  of  the  copper  carbonate  to  escape  into  the 
air,  since  this  chemical  is  not  only  irritating  to  the  eyes  and  the 
mucous  linings  of  the  nasal  passages,  but  is  poisonous. 

3.  Have  sufficient  capacity  for  the  amount  of  grain  to  be  treated 
in  the  time  available. 

4.  Clean  itself  completely  to  prevent  mixing  different  varieties 
of  seed.  This  is  important  particularly  in  custom  and  experimental 
work. 

Furthermore,  it  should  be  low  in  cost,  simple  in  construction,  dur- 
able, economical  of  power,  and  easy  to  operate,  and  its  repair  parts 
should  be  obtainable  within  a  reasonable  distance.  In  machines 
designed  to  treat  a  continuous  stream  of  grain,  the  proportioning  of 
dust  to  grain  should  be  secured  by  a  device  that  is  adjustable,  yet 
positive  in  its  action. 

Unsatisfactory  Machines.- — A  study  of  most  of  the  types  of 
machines  used  in  this  state  shows  that  many  of  them  are  unsatisfac- 
tory. Their  most  common  fault  is  their  inability  to  prevent  the  escape 
of  the  dust  into  the  air.  In  fact,  some  escapes  from  practically  every 
machine  in  use.  The  amount  depends  principally  upon  the  tightness 
of  the  walls  and  the  connections  of  the  mixing  chamber,  on  the  design 
and  construction  of  the  emptying  and  sacking  arrangements,  and  on 
the  correct  proportioning  of  dust  to  grain.  When  appreciable  amounts 
of  dust  escape  from  a  machine  used  indoors,  goggles  and  dust  masks 
should  be  used.  Both  of  these  devices  have  long  been  employed  in 
connection  with  various  manufactures  and  are  readily  obtainable.1 
A  mask  may  be  made  from  one  or  two  layers  of  thin  felt  or  heavy 
cotton  flannel,  lint  side  outward,  or  may  consist  merely  of  a  damp 
sponge.  However,  at  best,  a  mask  is  an  uncomfortable  thing,  especi- 
ally when  the  wearer  is  working.  There  is,  therefore,  always  a  temp- 
tation to  leave  it  off  and  risk  the  consequences.  Moreover,  some  kinds 
of  masks  are  ineffective,  affording  at  times  little  or  no  protection. 
Hence  it  is  much  better  to  prevent  the  escape  of  the  dust,  to  gather  it 
up  with  some  sort  of  a  vacuum  fan,  or  to  place  the  dusting  machine  in  a 
drafty  hallway  or  out  of  doors  and  use  it  only  when  there  is  a  good 
breeze  in  the  right  direction  to  blow  away  the  escaping  dust. 

Some  of  the  machines  tried  did  not  coat  the  seed  thoroughly, 
one  in  particular,  a  screw  conveyer  into  which  the  grain  and  dust 
were  fed.  Instead  of  mixing,  the  dust  settled  to  the  bottom  of  the 
stationary  conveyor  tube,  permitting  much  grain  to  be  discharged 
uncoated. 


1  Mackie,  W.  W.,   and  F.  N.  Briggs.     Fungicidal   dusts   for   the   control   of 
bunt.     California  Agr.  Exp.  Sta.  Bui.  364:563-504.     1923. 


BULL.  391]  MACHINES    FOR    COATING    SEED    WHEAT  5 

Batch  Mixers. — Mixers  of  this  type  are  given  a  measured  charge 
of  grain  and  a  proportionate  charge  of  the  dust.  The  machine  is 
closed  and  operated  for  the  requisite  time,  then  opened  and  the  grain 
permitted  to  run  out.  It  is  theoretically  possible  by  this  process  to 
secure  a  perfect  coating  of  dust  on  every  kernel  with  no  residue 
provided  the  proportioning  is  correct  and  the  time  of  operation 
sufficient.  Every  batch  mixer  studied  applied  the  dust  satisfactorily 
when  turned  long  enough. 


Fig.  2. — Barrel-type  dusting  machine,  designed  by  H.  E.  Drobish  and  H.  E. 
Paxton.  With  this  machine  one  man  and  a  boy  dusted  satisfactorily  8500  lbs. 
of  wheat  in  one  ten-hour  day.  Much  dust  escapes  when  resacking.  Best  speed 
about  45  r.p.m. 

In  a  batch  mixer  two  ounces  of  dust  are  used  for  each  bushel 
( 60  lbs. )  of  wheat.  One  may  be  tempted  to  increase  the  ratio  of  dust 
to  grain  in  order  to  secure  thorough  coating  in  less  time.  However, 
if  this  is  done,  three  difficulties  are  liable  to  arise:  (1)  excessive  dust 
puffing  out  through  the  sides  of  the  sack  while  the  treated  grain  is 
filling  it;  (2)  clogging  of  the  grain  drill  by  the  excess  of  dust;  (3) 
too  much  dust  in  the  air  when  an  end-gate  seeder  is  used.  Passing  the 
grain  over  a  suitable  screen  will  remove  the  excess.  Another  tendency 
is  to  put  in  too  large  a  batch  of  grain.  The  best  amount  is  a  volume 
of  about  one-fourth  to  one-third  the  space  inside  the  box,  according 
to  the  design.  Too  large  a  charge  makes  the  mixing  less  thorough  and 
somewhat  slower. 


6  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

A  rotary  barrel-type  churn  (fig.  2)  is  satisfactory  if  filled  about 
one-fourth  full  and  if  turned  slowly.  The  grain  must  fall  from  end 
to  end  (or  from  side  to  side)  of  the  churn. 

A  revolving  concrete  mixer  may  be  made  to  do  good  work,  but  is 
liable  to  permit  too  much  dust  to  escape,  even  though  the  openings  be 
covered  with  canvas  or  improvised  lids. 

A  tight  box  mounted  on  a  shaft  and  revolved  slowly  by  hand  or 
by  a  suitable  motor  or  engine  is  satisfactory.  (See  fig.  3.)  The 
revolving  box  of  figures  4  and  5  having  its  shaft  placed  diagonally, 
requires  more  space  up  and  down  and  a  slightly  stronger  supporting 
frame,  but  will  mix  much  more  rapidly  and  is  easier  to  empty  from 


Fig.  3. — Revolving  box  mixer,  A.  D.  Buffum,  Stratford,  California.  About 
250  lbs.  wheat  and  eight  ounces  dust  are  revolved  two  minutes  at  30  r.p.m.  in 
box  "A"  6  ft.  x  4  ft.  x  4  ft.  Grain  runs  out  by  hinged  door  "B"  into  hopper 
"D."  Sacked  through  chutes  "C"  Wagon  "E"  is  backed  to  mixer.  Mix- 
ing thorough.     Much  dust  escapes  on  emptying.     Two  h.p.  engine  is  used. 

the  corner  opening.  A  box  mixer  tightly  and  rigidly  built  and  painted 
in  the  joints  with  a  good  lead-oil  paint,  and  having  its  door  well  fitted 
and  firmly  closed,  permits  little  dust  to  sift  out  during  operation. 

The  mixer  shown  in  figures  4  and  5  is  too  large  for  the  greatest 
economy  either  in  construction  or  in  use.  A  cubical  shape  is  prefer- 
able to  the  oblong.  A  box  thirty  inches  each  way  inside  is  much 
cheaper  to  build  and  to  mount  and  is  easier  to  keep  from  racking.  It 
requires  about  one-half  as  much  power.  Also,  since  the  sides  are 
steeper,  the  treated  grain  runs  out  more  readily  at  the  low  corner.  If 
the  filling  is  done  by  hand  from  sacks,  the  smaller  machine  is  easier 
to  load. 


Fig.  4. — Diagonal  shaft  makes  mixer  more  effective.  Tight  construction 
and  direct  sacking  from  mixer  reduces  amount  of  dust  escaping.  Size  shown, 
3x3x5  ft.  inside.  Capacity  350  to  600  lbs.,  speed  33  r.p.m.,  requires  6  h.p. 
Thirty  inches  each  way  would  be  a  more  satisfactory  size  and  require  only  half 
as  much  power. 


Fig.  5. — Grain  inlet  of  diagonal  mixer.  The  neck  and  lid  of  a  discarded 
milk  can  were  found  satisfactory.  A  removable  sheet  metal  chute  is  supported 
on  the  iron  framework. 


8  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

If  a  box  mixer  is  to  be  used  for  several  seasons  it  should  be  housed 
in  a  dry  place  and  painted  at  least  once  in  three  years. 

To  prevent  racking  and  the  development  of  leaky  joints,  for  the 
size  shown  in  figure  4  the  box  should  be  made  of  at  least  %-inch 
tongue-and-grooved  flooring  of  the  best  quality.  The  nailing  and 
bracing  should  be  well  done,  and  only  well-seasoned  lumber  used. 


Fig.  5a. — Treated  grain  outlet  for  diagonal  box  mixer.  Canvas  tube  "K" 
surrounds  the  outlet.  Wooden  spring  "L"  holds  "K"  while  machine  turns. 
"M"  is  a  close-fitting  slide.  Sack  hangs  from  sackholder  "N"  and  is  sur- 
rounded by  sheet  metal  housing  "H."  A  vacuum  fan  draws  away  through- the 
opening  "  O"  any  dust  that  boils  out  through  sides  of  sack.  Fan  and  sack  housing 
not  needed  if  machine  is  used  in  a  good  draft. 


Continuous  Mixers,  Revolving  Type. — For  warehouse  and  ranch 
use  where  large  quantities  of  grain  are  to  be  treated,  the  batch  mixers 
are,  in  general,  of  too  small  capacity  and  require  too  much  labor  to 
be  satisfactory.  There  are  several  devices  in  use  which  receive  at  one 
end  a  stream  of  grain  and  dust  in  the  right  proportion,  and  discharge 
at  the  other  the  treated  grain.  These  are  of  two  kinds :  the  revolving 
type  and  the  gravity  type. 


Bull.  391] 


MACHINES    FOR    COATING    SEED    WHEAT 


Figure  6  shows  a  small  mixer  of  inclined  revolving  cylinder  type 
which  has  been  on  the  market  for  several  years.  It  allows  some  dust 
to  escape  and,  for  this  reason,  is  generally  used  out  of  doors.  A  later 
model  has  a  vacuum  fan  with  an  air  inlet  close  to  the  mouth  of  the 
pipe  which  discharges  the  treated  grain.  This  draws  some  of  the 
excess  dust  out  of  the  sack. 

It  was  found  that  some  users  of  machines  of  this  kind  had 
increased  the  slope  by  raising  the  hopper  end  so  as  to  hasten  the  flow 
of  the  grain  through  the  machine.  This  is  liable  to  result  in  imperfect 
coating. 


Fig.  6. — A  revolving  type,  continuous  mixer.  Driven  by  1  h.p.  motor, 
it  mixes  satisfactorily  about  1800  to  2500  lbs.  wheat  an  hour.  Allows  some 
dust  to  escape. 

Figure  7  shows  a  home-made  continuous  mixer  of  the  revolving 
cylinder  type  made  out  of  an  old  hot  water  tank  and  some  used  pulleys 
and  shafting.  Unless  care  and  skill  are  used  in  designing  and  con- 
structing such  a  machine,  too  much  dust  will  escape  into  the  air.  It 
is  possible  to  put  a  tight  housing  around  such  a  mixing  cylinder,  but 
its  construction  would  require  considerable  labor  and  skill. 

Figures  8  and  9  show  a  large  mixer  of  the  continuous  type  which 
is  constructed  somewhat  like  that  of  figures  6  and  7.  Unless  a  vacuum 
fan  is  used,  much  dust  escapes  into  the  air. 

In  figure  9  a  general  idea  is  given  of  the  inside  construction  of  the 
machine  of  figure  8.  As  will  be  observed,  there  are  two  sets  of  baffles 
inside  the  revolving  cylinder,  one  set  consisting  of  long  narrow  iron 
strips  placed  parallel  to  the  shaft,  the  other  of  short  plates  placed 
at  an  angle  with  the  shaft.     The  long  baffles  throw  the  grain  over 


10  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

and  over  and  tend  to  move  it  down  towards  the  outlet.  The  short 
baffles  tend  to  throw  the  grain  back  up  the  incline  away  from  the 
outlet,  thus  slowing  the  progress  of  the  grain  through  the  cylinder 
and  causing  more  thorough  coating. 

The  vacuum  fan  should  have  its  intake  connected  by  one  tube  to 
the  sack  housing  (not  shown)  and  by  another  to  the  top  of  the  grain 


Fig.    7. — Home-made    continuous    mixer    built    by    Mr.    Baker,    Richvale, 
California.     Treats  2500  lbs.  wheat  an  hour.     Much  dust  escapes. 

receiving  bin.  Each  tube  should  have  a  regulating  valve  or  damper. 
Drawing  air  from  the  grain  bin  causes  air  to  enter  through  all  the 
chinks  and  open  joints  of  the  machine  and  thus  prevents  the  escape 
of  dust. 

Generally  speaking,  in  revolving-type  mixers  the  design  of  the 
interior  of  the  revolving  members  may  differ  quite  widely  with  a 
correspondingly  wide  difference  in  effectiveness.  The  mixer  of  figures 
4  and  5  requires  no  baffles,  since  the  oblique  placing  of  the  shaft 


Fig.  8. — Continuous,  revolving  cylinder  type,  used  at  the  W.  D.  Lewis  grain 
warehouse,  Guernsey,  California.  Grain  from  chute  runs  into  hopper  "A," 
where  dust  from  proportioning  device  "B"  is  added.  Grain  and  dust  run 
into  upper  end  of  revolving  steel  cylinder  "C."  Treated  grain  falls  into  bin 
"E, "  thence  into  sacks.  Hand  wheel  "D"  adjusts  flow  of  grain.  Much  dust 
escapes  unless  a  vacuum  fan  is  used.  Mixing  satisfactory.  Capacity  about  7500 
lbs.  wheat  an  hour. 


Copper  Carbor 


Fig.  9. — Section  sketch  of  the  mixer  of  figure  8. 


12 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


causes  the  grain  to  be  thrown  to  both  right  and  left  parallel  to  the 
shaft,  and,  at  the  same  time,  to  be  rolled  over  and  over.  The  machines 
of  figures  2  and  3  should  have  baffles  similar  to  those  in  a  revolving 
concrete  mixer.  They  should  be  so  placed  as  not  to  hinder  too  much 
the  outflow  of  the  treated  grain.  The  height  of  any  baffle  should  not 
exceed  one-sixth  of  the  diameter  of  the  cylinder  (or  of  the  width  of 
a  side). 


h 3'0'- 


Cr&jv  <3ecf/on 


Patented 


Fig.  10. — A  gravity-type  mixer  (section  view).  Grain  thrown  from  side  to 
side  by  baffles,  falls  through  cloud  of  dust  circulated  by  blower.  Excess  dust 
drawn  out  through  screen  and  re-circulated.  The  pipes  broken  away  indicate 
that  the  mixer  may  be  placed  out  of  doors  and  the  motor  inside.  "A"  and 
' f  A' ' '  are  alternative  dust  proportioned. 


The  speed  of  rotation  must  be  carefully  chosen  to  fit  the  size.  If 
the  speed  is  too  high,  it  will  cause  the  centrifugal  effect  to  overcome 
the  gravity  effect  on  the  grain  and  prevent  satisfactory  operation, 
while  if  too  slow,  it  will  reduce  the  capacity  of  the  machine.  The 
speed  that  requires  the  most  power  and  produces  the  most  violent 
tumbling  about  of  the  grain  is  the  best.     This  applies  to  all  machines 


Bull.  391] 


MACHINES    FOR    COATING    SEED    WHEAT 


13 


having  a  revolving  mixing  chamber.     The  larger  the  diameter  of  the 
revolving  part  the  slower  must  be  the  speed.    See  figures  2,  3  and  4. 

Continuous  Mixers.  Gravity-Type. — Figures  10  and  11  show  a 
patented  gravity-type  mixer.  This  machine  has  a  vertical  chute 
through  which  the  grain  falls.  Sloping  baffle  plates  attached  to  two 
opposite  walls  cause  the  grain  to  be  thrown  from  side  to  side  as  it 
falls.     The  copper  carbonate  is  applied  as  a  dust  cloud  surrounding 


Section  a/-  A- A 


Detail  of  Screen 


Fig.  11. — The  gravity-type  mixer  of  figure  10,  side  and  section  views. 
Tight  construction  is  essential.  With  proper  construction  mixing  is  satisfactory 
and  little  dust  escapes  into  the  air.  Capacity  about  9000  lbs.  an  hour  for  the 
size  shown. 


the  falling  grain.  Air  and  dust  are  circulated  downward  through 
the  mixer  chute  by  the  use  of  a  blower.  This  machine  requires  less 
chemical  than  most  others  because  it  draws  out  the  excess  dust 
through  a  screen  at  the  bottom  and  recirculates  it. 

The  capacity  depends  on  the  width,  breadth  and  height  of  the 
vertical  chute.  One  of  these  machines  measuring  over  all  13  feet 
high,  and  2  feet  by  4  feet  (inside,  9  ft.  6  in.  high  and  1  ft.  9  in.  x  3  ft.) 
treats  9000  lbs.  an  hour. 


14 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


The  slope  of  the  inclined  baffles  should  be  steep  enough  to  cause 
the  grain  to  fall  readily  and  the  machine  to  clean  itself  completely. 
Dusted  grain  will  lodge  on  a  much  steeper  slope  than  untreated  grain. 

When  the  proportioning  device  A  (fig.  10)  was  used,  the  feed  of 
dust  was  found  to  be  irregular,  and  the  coating  of  the  grain  non- 
uniform.   Also  considerable  dust  escaped  whenever  the  dust  feed  was 


Dust  chute 
Wood  ctamp  atr/p* 


y=  YV'nhen  "W/s 

•Smo/t    Ate  rer 

more    than  J'O* 


Fig. 


ffina 


12. — A  mixer  of  the  plain  gravity-type.      Sack  housing   and   vacuum   fan 
are  unnecessary  if  machine  is  used  in  a  good  draft. 


momentarily  too  rapid.  If  a  positive  action  dust  feeder  such  as  A' 
is  used  with  this  machine,  the  coating  should  be  satisfactory,  with 
little  excess  of  dust  left  with  the  treated  grain  or  escaping  into  the 
air. 

A  mixer  of  the  plain  gravity-type  without  means  for  circulating 
dusty  air  around  the  falling  grain  was  found  in  use  on  a  ranch  in  this 
state.  Its  approximate  construction  is  shown  in  figure  12.  An  ordin- 
ary bucket-type  elevator  raised  the  grain  from  a  dump  pit  to  the  top 


Bull.  391] 


MACHINES   FOR    COATING   SEED   WHEAT 


15 


of  the  mixer.  A  dust  proportioning  device  somewhat  similar  to  A' 
of  figure  10  was  located  at  the  top  of  the  mixing  chute  and  its  shaft 
driven  from  the  top  shaft  of  the  elevator.  The  baffles  were  flat 
instead  of  the  alternating  V-  and  inverted  V-shape  shown  in  the 
figure.  Considerable  dust  escaped  because  of  loose  joints  and  inade- 
quate provision  for  taking  care  of  the  out-rush  of  air  while  the  receiv- 
ing bin  at  the  bottom  was  filling  with  grain  during  the  changing  of 
sacks. 

The  cloth  construction  indicated  as  surrounding  the  dust  and  grain 
tubes  as  they  enter  the  top  of  the  mixing  chute  acts  as  a  breather 


Fig.  13. — Combination  of  re-cleaning  and  dusting  saves  time  and  labor. 
One  gas  engine  drives  both  these  machines. 

equalizing  the  air  pressure  but  preventing  the  escape  of  dust.  Thin 
felt  or  heavy  eiderdown  blanketing  is  better  than  cotton  flannel.  A 
ribbon  of  cotton  flannel  or  felt  should  be  placed  in  such  joints  as 
might  leak.  Knot  holes  may  be  closed  by  the  use  of  cotton  waste  or 
rags  moistened  with  shellac  varnish  and  tamped  in  securely. 

Redeeming  and  Dusting. — Figure  13  indicates  how  time,  labor, 
and  power  may  be  economized  by  recleaning  and  dusting  in  the  same 
operation.  The  outfit  shown  was  belted  to  a  stationary  gas  engine 
of  about  3  h.p. 

Collecting  Escaped  Dust.- — Usually  much  dust  boils  out  through 
the  sides  of  the  sack  while  the  treated  grain  is  running  out  of  a  mixer 
of  any  type.  A  vacuum  cleaner  or  suction  fan  drawing  its  air  from 
a  sheet  metal  or  wooden  housing  surrounding  the  sack  will  take  care 
of  this  dust.     The  air  discharged  from  the  fan  may  be  piped  outside 


16  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

or  may  be  cleansed  by  passing  through  the  ordinary  vacuum  cleaner 
bag  or  through  one  made  of  a  suitable  felt.  The  dust  caught  may  be 
used  again.  Except  in  large  commercial  dusting  operations  the  small 
amount  of  dust  caught  will  not  be  worth  the  trouble  to  recover  it. 
However,  if  left  to  float  about  the  room,  a  small  fraction  of  an  ounce 
might  cause  much  distress  to  a  person  breathing  it. 

Treated  Grain  Dangerous. — After  working  with  copper  carbonate 
or  treated  grain,  the  hands  should  be  thoroughly  washed  before  touch- 
ing food.  The  treated  grain  is  poisonous  to  livestock  of  all  kinds  as 
well  as  to  rodents.    Weevils  also  are  unable  to  live  in  it. 

Manufacturers  of  Dusting  Machines. — The  Agricultural  Engineer- 
ing Division,  College  of  Agriculture,  University  of  California,  Davis, 
California,  will  furnish  manufacturers'  addresses  on  request. 


BIBLIOGRAPHY 

Heald,  F.  D.,  and  L.  J.  Smith. 

1922.  The  dusting-  of  wheat   for  bunt   or   stinking  smut.     Washington   Agr. 

Exp.  Sta.  Bui.  171:1-28. 
Mackie,  W.  W. 

1919.      Seed  treatment   for  the  prevention   of   cereal   smuts.      California   Agr. 

Exp.  Sta.  Cir.  214:1-8. 
Mackie,  W.  W.,  and  F.  N.  Briggs 

1923.  Fungicidal  dusts  for  the  control   of  bunt.     California  Agr.  Exp.  Sta. 

Bui.  364:531-572. 
Melchern,  L.  E.,  and  H.  B.  Walker 

1924.  The  copper  carbonate  method  of  controlling  bunt  of  wheat.     Kansas 

Agr.  Exp.  Sta.  Cir.  107:1-14. 
Stakman,  E.  C,  and  E.  B.  Lambert 

1923.     Dusting  seed  grain  to  prevent  smut,     Minnesota  Agr.  Extension,  Special 
Bui.  70:1-12. 


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